Methods and apparatuses for cold plasma in agriculture

ABSTRACT

Methods and systems for generating a plasma-activated liquid or gas, and applying the plasma-activated liquid for agricultural use. A system embodiment includes a hand-held device that can be pointed and directed at different target areas of a plant. A method embodiment includes generating a plasma discharge in a gas environment or a liquid environment, and applying the gas/liquid to a plant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/191,298, filed Nov. 14, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/585,957, filed Nov. 14, 2017, eachof which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an apparatus and a method for applyingplasma-activated liquids and gases to plants and in agriculturalsettings.

BRIEF SUMMARY OF THE INVENTION

In an embodiment, a method for production of plasma-activated liquids isdescribed. The method includes immersing a first electrode and a secondelectrode into liquid in a container, and energizing, by a high voltagepower supply, the first electrode and the second electrode to form aplasma between the first electrode and the second electrode to therebygenerate plasma-activated liquid. The method also includes etchingmaterial from at least one of the first electrode and the secondelectrode into the plasma-activated liquid.

In another embodiment, a method for applying plasma gas to plants isdescribed. The method includes passing a gas through a dielectriccylinder from one end to another end, and energizing, by a high voltagepower supply, an inner electrode and an outer electrode to generate theplasma gas from the gas, wherein the inner electrode is disposed insideof the dielectric cylinder and the outer electrode circumscribes anoutside of the dielectric cylinder. The method includes delivering theplasma gas to a plant.

In yet another embodiment, a system is described that is configured toapply plasma gas in an agricultural setting. The system includes adielectric cylinder having a proximal end and a distal end, as well asan inner electrode disposed inside of the dielectric cylinder, and anouter electrode circumscribing an outside of the dielectric cylinder.The system further includes one or more pipes coupled to the dielectriccylinder, the inner electrode and the outer electrode, the one or morepipes configured to source gas to the proximal end of the dielectriccylinder for flow through to the distal end, and wherein the one or morepipes are further configured to support wiring to the inner electrodeand the outer electrode. The system also includes a high voltage powersupply coupled to the wiring to provide energy to thereby generate theplasma gas from the gas, as well as an outlet coupled to the distal end,the outlet being configured to apply the plasma gas in the agriculturalsetting.

Further features and advantages, as well as the structure and operationof various embodiments, are described in detail below with reference tothe accompanying drawings. It is noted that the specific embodimentsdescribed herein are not intended to be limiting. Such embodiments arepresented herein for illustrative purposes only. Additional embodimentswill be apparent to persons skilled in the relevant art(s) based on theteachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments of the present disclosureand, together with the description, further serve to explain theprinciples of the disclosure and to enable a person skilled in thepertinent art to make and use the embodiments.

FIG. 1 illustrates an apparatus having an electrically insulativecontainer of water in which a silver plate anode is placed in proximityto a carbon graphite rod, according to an embodiment of the presentdisclosure.

FIG. 2 illustrates an apparatus having an electrically insulativecontainer of water in which two carbon graphite rods are placed,according to an embodiment of the present disclosure.

FIG. 3 illustrates a plasma discharge grid used to generate plasma in agaseous environment, where the gas plasma is directed towards a plant toreduce the growth of plant pathogens, according to an embodiment of thepresent disclosure.

FIG. 4 illustrates a method for applying a plasma-activated liquid to aplant, according to an embodiment of the present disclosure.

The present disclosure will be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

The following Detailed Description refers to accompanying drawings toillustrate exemplary embodiments consistent with the disclosure.References in the Detailed Description to “one exemplary embodiment,”“an exemplary embodiment,” “an example exemplary embodiment.” etc.,indicate that the exemplary embodiment described may include aparticular feature, structure, or characteristic, but every exemplaryembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same exemplary embodiment. Further, when a particularfeature, structure, or characteristic is described in connection with anexemplary embodiment, it is within the knowledge of those skilled in therelevant art(s) to affect such feature, structure, or characteristic inconnection with other exemplary embodiments whether or not explicitlydescribed.

The exemplary embodiments described herein are provided for illustrativepurposes, and are not limiting. Other exemplary embodiments arepossible, and modifications may be made to the exemplary embodimentswithin the spirit and scope of the disclosure. Therefore, the DetailedDescription is not meant to limit the invention. Rather, the scope ofthe invention is defined only in accordance with the following claimsand their equivalents.

The following Detailed Description of the exemplary embodiments will sofully reveal the general nature of the invention that others can, byapplying knowledge of those skilled in relevant art(s), readily modifyand/or adapt for various applications such exemplary embodiments,without undue experimentation, without departing from the spirit andscope of the disclosure. Therefore, such adaptations and modificationsare intended to be within the meaning and plurality of equivalents ofthe exemplary embodiments based upon the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by those skilled in relevant art(s) in light of theteachings herein.

Disclosed herein are apparatuses and methods for generating and applyingplasma-activated liquids to plants, soil or water reservoirs to alterplant growth (i.e., influence growth rate, reduce time to maturity orharvest), increase plant yield, improve plant health and/or mitigatepathogens.

The following embodiments of generating and applying a plasma-activatedliquid are meant to serve as exemplary only and are not intended tolimit the scope of the inventive concept. It will be apparent to personsskilled in the relevant art that various changes in form and detail canbe made therein without departing from the spirit and scope of theinvention. Thus, the breadth and scope of the present invention shouldnot be limited by and of the described exemplary embodiments herein.

A specific example of a system and method of generating aplasma-activated liquid and applying the plasma-activated liquid isdescribed below, followed by other variables that may be incorporatedinto this system and method. In various embodiments, two electrodescomposed of graphite are submerged into a container of water. In oneembodiment, the water can be 250 ml distilled water at 95° C., althoughthese values are for illustrative purposes. In various embodiments, theshape of the graphite electrodes can be substantially cylindrical (i.e.,rod shaped, but this is not intended to be limiting, as spherical,conical, planar, and other electrode shapes are contemplated) in crosssection. In a particular embodiment, the cross section of the electrodeshas a diameter of approximately 6 mm and a length of approximately 25mm. One of the electrodes is electrically coupled to earth ground usinga wire. The other electrode is electrically coupled to the output of ahigh voltage radio frequency (RF) power supply. In one embodiment, theRF power supply is configured to generate approximately 30 kV peak topeak RF voltage, at multiple simultaneous frequencies that are primarilyconcentrated between 200 and 600 kHz. In this embodiment, the RF powersupply is further pulsed on and off at 500 Hz. The distance between thetwo electrodes is adjusted until a bright electrical arc (plasmadischarge) is sustained. In one particular embodiment, the distancebetween the two electrodes is approximately 1 mm to 4 mm. The distancebetween the electrodes is periodically adjusted to maintain the arcsince material is etched from the electrodes into the liquid. In variousembodiments, the electrodes are held in a fixture that allows thedistance to be finely controlled by turning a knob and gear assembly.

Various embodiments use predetermined times of arcing. For example, thearcing can be sustained for approximately 5 minutes, 10 minutes, or 30minutes, or until the desired amount of carbon is suspended in theliquid or until a desired chemistry of water is achieved. A desiredchemistry of water (or liquid) may include the water (liquid) reached adesired measured property, such a level of reactive oxygen species (ROS)produced, acidity level, level of free radicals, and the like. Invarious embodiments, the electrode material (e.g., carbon) is filteredout of the solution. In some embodiments, the filtering of the electrodematerial is necessary because the solution becomes more conductive aselectrode material is etched and suspended in the liquid. At some point,the plasma are is not generated/sustained because the liquid has becometoo conductive. In some embodiments, the filtered electrode material maybe a useful by-product of the processes described above. Thiscarbon-enriched plasma-activated liquid is then mixed with a standardplant nutrient solution in approximately a 1:10 ratio. The carbonenriched nutrient solution is then applied to growing plants throughdirect application (e.g., watering when the liquid is water), or isintroduced into the reservoir of a hydroponic delivery system. Over thecourse of 1-4 weeks of periodic carbon-enriched water application (1-2times per week), the plants grow more vigorously (taller, broader,increased root development) and achieve a significantly higher harvestmass than plants watered with a comparable nutrient solution in acontrolled experiment. The following features and descriptions applymore generally to the specific system and method described above:

More generally, other embodiments have a device that has at least twoelectrodes energized by a high voltage power supply. The electrodes aresubmerged in a liquid, an electrical gradient is applied between theelectrodes that leads to the generation of an electrical arc, wherebythe electrical arc leads to removal and deposition of the electrodematerial into the liquid. In various embodiments, the liquid can bedistilled water, tap water, or an ion rich solution such as a nutrientsolution for plant growth.

The electrodes in various embodiments are composed of a conductivematerial, where the conductive material is selected from graphite,tungsten, silver, gold, titanium, copper or similar materials. Invarious embodiments, the two electrodes may be composed of the samematerial, and that such material may be selected based on its impact onplant biology. In other embodiments, the two electrodes may be composedof different materials, and that each material may be selected based ona number of factors including impact on plant biology. As noted above,electrode material is deposited in the solution, and is suspended in thesolution at micro-sized and nano-sized particles. The removal of theelectrode material from the electrodes may be achieved as a result ofelectrical etching. In certain embodiments, the suspended electrodematerial(s) may generate chemical reactions or physical interactions,such as absorption with the liquid contents, or between the liquidcontents and the electrode material. For example, nutrients may beadsorbed on the surface on the electrode material (e.g., carbon) afterthe electrode material is produced during the plasma-activated liquidproduction. Those chemical reactions may be assisted by the applicationof electrical energy.

Embodiments include a power supply to provide the electrical energy.Various power supplies may be used, including a DC power supply, apulsed DC power supply (exemplary pulse widths include microsecond,millisecond and nanosecond pulse widths), alternating current (AC) powersupply, a pulsed AC power supply, an RF power supply, a pulsed RF powersupply, and a power supply that provides microwave energy. Otherembodiments of power supplies include an AC power supply that providesmultiple harmonic-rich frequencies that are generated simultaneously.

In embodiments, the power supply provides energy to one of theelectrodes, while the other electrode may be grounded. Alternatively,the other electrode may be a node for supply of an opposing phase of analternating current waveform. In various options, the opposing phase maybe a substantially equal and opposite potential to that of the firstelectrode, of a lower amplitude of an opposing alternating currentwaveform, or a lower amplitude of an in-phase alternating currentwaveform.

As noted above, embodiments may be used in agriculture, including theapplication of plasma-activated liquids to plants. In variousapplications, the plants include vegetables, fruits, medicinal,ornamental, and algae. Plants are grown in a variety of growth media,including: soil, soilless mixes (coconut fiber, perlite, vermiculite),sphagnum moss, rockwool, clay pellets, water absorbing polymers, andother media generally known in the art. Application of theplasma-activated liquids incudes application in the root zone or on thefoliage of the plants. Root zone application includes watering usingdirect watering, drip irrigation, and hydroponic irrigation methods.Foliage applications includes spraying, misting, ultrasonic atomization,electro-spraying and similar approaches.

The plasma-activated liquid application offers various benefits,including the improvement of plant growth, root structure, leaf quality,fruit quality, flower quality, and/or plant yield. Benefits also includeimprovement of the growth rate of the plant (i.e., a reduced time tomaturity or harvest). Other benefits also include the destruction ofpathogens, where the pathogens may include fungus, oomycetes, bacterium,and viruses. Specific examples of pathogens may include powdery mildew,Fusarium, Botrytis, tobacco mosaic virus, and the like.

Certain benefits may be coordinated with certain aspects of certainembodiments. For example, the electrode material introduced to theliquid may be selected to achieve the desired biological effect and inaccordance with the particular application method used (i.e., root zonevs. foliage). In a specific example, a graphite material may be selectedto improve plant growth and yield when liquid is applied to the rootzone. In another example, a silver material may be selected to destroypathogens when liquid is applied to the root zone or foliage.

Embodiments of plasma-activated liquid generation apparatus includestand-alone systems, as well as integrated applications. A stand-alonesystem embodiment may be used to produce plasma-activated liquid (e.g.,water), which is then “bottled” for future use for plants. An integratedapplication includes use in an existing agricultural grow facility,where the plasma-activated liquid (e.g., water) is directly pumped ordirectly flows into the grow facility and administered to the plants. Inany of these embodiments, the plasma-activated liquid may be firstdiluted into water or nutrient solutions. Another integrated applicationincludes use in an agricultural farm or field, where theplasma-activated liquid (e.g., water) is directly pumped or directlyflows into the farm or field and administered to the plants. In any ofthese embodiments, the plasma-activated liquid may be first diluted intowater or nutrient solutions.

Other embodiments include methods of generating a plasma-activatedliquid. In an exemplary embodiment, the method includes immersing two ormore electrodes in a solution, applying a difference in high voltagepotential to the two or more electrodes, generating an electrical arcbetween the two or more electrodes, removing electrode material from oneor more electrodes into the liquid, and applying the liquid to a plant.In one embodiment, applying the liquid to a plant includes applying theliquid to the root zone of the plant. In another embodiment, applyingthe liquid to a plant includes applying the liquid to the foliage of theplant. In various alternative embodiments, the liquid is mixed withother liquids prior to application to the plant. In embodiments, theother liquids include water, and a nutrient solution suitable to sustainplan growth. In a further embodiment, the method includesplasma-activating a liquid(s) to change the properties of the liquid(s)to be nutritionally superior for the purpose of improving plant growthcycle, health, immunity and/or yield.

In a further embodiment of generating a plasma for agricultural use, aplasma discharge is generated in a gaseous environment and the gasplasma is directed towards a plant to reduce the growth of plantpathogens. In one exemplary embodiment, an inner electrode is placedinside of a cylinder made of a dielectric material. A ring-shaped outerelectrode circumscribes the outside of the dielectric cylinder, and thering-shaped electrode is connected to earth ground. In an exemplaryembodiment, the ring-shaped electrode is approximately 55 m in diameter.The inner electrode consists of a dielectric coated conductive materialand is connected to a high voltage power supply. By way of example, thedielectric material may be glass and the electrode may be created by aconductive paint applied to the inner walls of a sealed-end glasscylinder. In a particular example, the inner electrode is approximately15 mm in outside diameter, and there is a space of approximately 20 mmbetween the outside diameter of the inner electrode and inside diameterof the dielectric cylinder wall. A gas is made to flow through thedielectric cylinder from one end to the other. The inner electrode isenergized with a high voltage RF electrical energy source therebygenerating an electrical discharge between the outside diameter of theinner electrode dielectric and the inside diameter of the outerelectrode dielectric. In a particular example, the high voltage RFelectrical energy source is approximately 35 kV peak to peak. Thiselectrical discharge ionizes the gas passing through the cylindergenerating a plasma. By way of example, the gas may be air. A hose orother means of delivery may be attached to the distal end of the plasmagenerating cylinder. An air pump or fan may be used to flow air throughthe core of the cylinder and through the discharge zone where ionizationtakes place. The flow of air pushes the plasma out of the distal end ofthe device. The reactive chemical species, such as reactive oxygenspecies and reactive nitrogen species, exit the distal end of the plasmagenerating cylinder. These reactive species, along with other chargedspecies from the plasma discharge, are sprayed onto a plant surface. Theplasma discharge interacts with microbes on the surface, or subsurface,of the plant rendering them nonviable. This system has demonstratedeffectiveness on a range of fungal and bacterial strains that commonlyinfect plants and have a negative impact on the agriculture industryincluding; powdery mildew, Botrytis, and E. coli. It should beappreciated that the destruction of these pathogens would be valuable atall stages of plant production including, seeds, seedlings, growingplants, and the sanitation of agricultural products after harvest.

The above system embodiments may be easily configured in a hand-helddevice that can be pointed and directed, by a human or automatedactuator, at different target areas of a plant. The power supply may bebackpack mounted or cart mounted to allow for a lightweight andmaneuverable hand-held plasma applicator. In an alternate embodiment, acentrally located power supply may be used to power smaller plasmagenerators that are dispersed around an agricultural facility in arrays,such that activating the system will deliver plasma-activated gas to alarge area of growing plants simultaneously. This could be used to“blanket” and area in plasma-activated gas and sanitize large areas.

As would be appreciated by one skilled in the art, the apparatusdescribed above may be modified in several ways yet still achieve theintended purpose. For example, the dielectric materials may be glass,ceramic, PTFE, Delrin, or other well-known plastic dielectric materials.The electrode materials may be copper, tungsten, carbon, or conductivepaints/coatings. The diameters of the inner and outer cylinders could bealtered, as long as the distance between the two remained sufficient tosustain a plasma discharge at the applied voltage. The waveform ofapplied voltage could be modified, e.g. DC, pulsed DC, AC, RF, pulsedRF, and microwave of different frequencies. The earth ground electrodecould be connected to an alternating phase of the power supply. Multiplering-shaped electrodes could be introduced to the outer cylinder inorder to control the pattern of plasma generated. Of the multiplering-shaped electrodes, only certain electrodes may be connected toearth ground, and/or to an alternating phase of the power supply, inorder to further control the plasma generation. The flow rate of gascould be altered to achieve the desired concentration of reactivespecies based on dwell time in the plasma chamber. The gas compositioncould be modified to include noble gases such as helium or argon, couldbe enriched with oxygen or nitrogen, or combinations thereof.

Embodiments include a method of treating plant pathogens using a plasmareactor chamber that contains at least two electrodes, whereby energy ispassed between the at least two electrodes, a gas is passed through theplasma reactor chamber, the outflow port is directed at a plant which iscolonized by a pathogen, and the pathogen is reduced in number orviability by the plasma gas outflow.

Embodiments include a method of generating a plasma-activated liquid forapplication to a plant whereby an electrical arc is generated in acontainment chamber as described above, a gas is passed through thecontainment chamber, the gas is bubbled through a liquid, the liquid isthen applied to a plant. A porous stone may be used to increase thesurface area of the gas bubbling through the liquid. The liquid mayconsist of pure water or may contain other chemicals or dissolved salts.In one embodiment, the liquid contains potassium bicarbonate and theplasma-activated liquid is used for foliar application to growingplants. In another embodiment, the liquid contains hydrogen peroxide(e.g., 1% hydrogen peroxide) and after plasma bubbling is used forfoliar application. In a third embodiment, the liquid contains coppersalts and is applied to the root zone for the treatment of fungus.

FIG. 1 illustrates is an apparatus having an electrically insulativecontainer of water in which a silver plate anode is placed in proximityto a carbon graphite rod, according to an embodiment of the presentdisclosure. In FIG. 1 , a container 140 contains a liquid 150. Immersedin liquid 150 are two electrodes, cathode 110 and anode 120. In anembodiment, cathode 110 is made of graphite, and anode 120 is made ofsilver. When cathode 110 and anode 120 are energized, a plasma discharge130 is formed.

FIG. 2 illustrates is an apparatus having an electrically insulativecontainer of water in which two carbon graphite rods are placed,according to an embodiment of the present disclosure. Container 230contains water 240 (or another liquid). Immersed in water 240 are twoelectrodes 210, which in an embodiment are carbon graphite rods. Whenelectrodes 210 are energized, a plasma 220 is formed.

FIG. 3 illustrates a plasma discharge grid used to generate plasma in agaseous environment, where the gas plasma is directed towards a plant toreduce the growth of plant pathogens, according to an embodiment of thepresent disclosure. In this embodiment, a pipe system 310 is used todeliver electrical energy and gas to plasma gas distribution points 320for application to plants 330. Plants 330 are being grown in soil 350.Pipe system 310 receives the electrical energy from power supply 360.Pipe system 310 receives gas from a gas supply (not shown).

FIG. 4 illustrates a method for applying a plasma-activated liquid to aplant, according to an embodiment of the present disclosure. In step410, a first electrode and a second electrode is immersed into liquid ina container. In step 420, the first electrode and the second electrodeare energized by a high voltage power supply to form a plasma betweenthe first electrode and the second electrode to thereby generateplasma-activated liquid. In step 430, material is etched from at leastone of the first electrode and the second electrode into theplasma-activated liquid. In step 440, the plasma-activated liquid andetched material is applied to a plant.

It will be apparent to those skilled in the relevant art(s) that variouschanges in form and detail can be made therein without departing fromthe spirit and scope of the disclosure. Thus, the disclosure should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for production of plasma-activatedliquids, the method comprising: immersing a first electrode and a secondelectrode into liquid in a container; energizing, by a high voltagepower supply, the first electrode and the second electrode to form aplasma within the liquid and between the first electrode and the secondelectrode to thereby generate plasma-activated liquid; and etchingmaterial from at least one of the first electrode and the secondelectrode into the plasma-activated liquid.
 2. The method of claim 1,wherein the liquid is one of water, distilled water, ornutrient-enriched liquid.
 3. The method of claim 1, wherein energizingby the high voltage power supply includes energizing by a DC powersupply, an AC power supply, a pulsed DC power supply, a pulsed AC powersupply, a harmonic RF power supply, or a RF power supply operating atmicrowave frequencies.
 4. The method of claim 1, further comprisingapplying the plasma activated liquid to a plant.
 5. The method of claim4, wherein applying the plasma-activated liquid to a plant includesapplying the plasma-activated liquid to a root zone of the plant.
 6. Themethod of claim 4, wherein applying the plasma-activated liquid to aplant includes applying the plasma-activated liquid to foliage of theplant.
 7. The method of claim 4, wherein reactive species within theplasma-activated liquid interact with one or more microbes on the plantto render the one or more microbes nonviable.
 8. The method of claim 4,wherein the first electrode comprises graphite, and wherein the secondelectrode comprises silver.
 9. The method of claim 4, wherein theplasma-activated liquid is introduced into a reservoir of a hydroponicdelivery system, and wherein the hydroponic delivery system applies theplasma-activated liquid to the plant.
 10. The method of claim 1, furthercomprising: filtering the etched material from the plasma activatedliquid; and applying the filtered etched material to a plant.
 11. Themethod of claim 1, further comprising: filtering the etched materialfrom the plasma activated liquid; and after filtering of the etchedmaterial, applying the plasma activated liquid to a plant.
 12. Themethod of claim 1, further comprising: mixing the plasma-activatedliquid with a second liquid; and applying the mixed plasma activatedliquid to a plant.
 13. The method of claim 1, further comprisingadjusting a position of at least one of the first electrode and thesecond electrode to maintain the plasma between the first electrode andthe second electrode.
 14. The method of claim 1, wherein energizing, bythe high voltage power supply, the first electrode and the secondelectrode occurs for a predetermined period of time.
 15. The method ofclaim 1, wherein energizing, by the high voltage power supply, the firstelectrode and the second electrode occurs until a desired chemistry ofliquid is achieved.
 16. The method of claim 1, wherein the firstelectrode comprises graphite.
 17. The method of claim 16, wherein thesecond electrode comprises silver.
 18. The method of claim 16, whereinthe second electrode comprises graphite.
 19. The method of claim 1,wherein the first electrode comprises graphite, tungsten, silver, gold,titanium, or copper, and wherein the second electrode comprisesgraphite, tungsten, silver, gold, titanium, or copper.
 20. The method ofclaim 1, wherein the first and second electrodes are spaced apart by 1mm to 4 mm.